Previously, if a PTR query is seen for a non-existing record, we'd
generate an empty response (but not NXDOMAIN or so). Fix that. If we
have no data about an IP address, then let's say so, so that the
original error is returned, instead of anything synthesized.
Fixes: #6543
Let's ensure that "no gateway" translates to "no domain", instead of an
empty reply. This is in line with what nss-myhostname does in the same
case, hence let's unify behaviour here of nss-myhostname and resolved.
This changes the symbolic name for the default gateway from "gateway" to
"_gateway". A new configuration option -Dcompat-gateway-hostname=true|false
is added. If it is set, the old name is also supported, but the new name
is used as the canonical name in either case. This is intended as a temporary
measure to make the transition easier, and the option should be removed
after a few releases, at which point only the new name will be used.
The old "gateway" name mostly works OK, but hasn't gained widespread acceptance
because of the following (potential) conflicts:
- it is completely legal to have a host called "gateway"
- there is no guarantee that "gateway" will not be registered as a TLD, even
though this currently seems unlikely. (Even then, there would be no
conflict except for the case when the top-level domain itself was being resolved.
The "gateway" or "_gateway" labels have only special meaning when the
whole name consists of a single label, so resolution of any subdomain
of the hypothetical gateway. TLD would still work OK. )
Moving to "_gateway" avoids those issues because underscores are not allowed
in host names (RFC 1123, §2.1) and avoids potential conflicts with local or
global names.
v2:
- simplify the logic to hardcode "_gateway" and allow
-Dcompat-gateway-hostname=true as a temporary measure.
When we synthesize A/AAAA for domains like "localhost", then make sure we generate ENODATA if the user asks for RR
types such a RP to be solved on the name. Previously, we'd pass the error back in that case that was generated from the
usual lookup procedure.
